Production of magnetizable alloy



Patented Mar. 30,

7 mam 'rnonuc'riouj F MAGNE'rizABLn ALLOY Albert Heinzel. Oppau, and Franz Duf tschmid,

Heidelberg, Germany, a'sslsnors to I. G. Far-benindustrie Aktiengcsellschaft, Frankfort-on-the- Main, Germany No Drawing. I Application August 31, iasaIsei-ni No. 38,788. Germany September 4, 1934 9 Claims. (01. 148-415) slight cold working effected by simply unwinding annealing, then subjecting them to a slight cold 10 working, advantageously of less than 20 per cent, to bring them to their final thickness and then subjecting them to a final annealing, preferably at temperatures above 700 C. The process according to this invention is especially suitable 15 for the preparation of highly magnetic alloys of iron and nickel alone, in particular for those containing from 40 to 50 per cent of nickel and from 60to 50 per cent of iron, but may also be employed for nickel-iron alloys having one or more 20 other components in minor quantities, as for example cobalt, aluminium, silicon, titanium, chromium, molybdenum, tungsten, copper or manganese.

Especially favourable results are obtained when 25 the first cold working is very strong, as for example amounting to from 80 to 90 per cent, and the cold working before the final annealing is not much stronger than the cold working above which a recrystallization is caused by annealing. For example a. cold working of per cent after a cold working of 80 per cent effects an increase of the initial permeability to three times the value, and a working of per cent after a working of 80 per cent doubles the initial permeability which is obtained without employing the slight additional cold working.

A special improvement in the magnetic quality is obtained when the alloys, in contrast to the manner of working hitherto adopted, are not not working, as for example after the hot rolling,

i. e. before the first cold working according to this invention.

Nickel-iron alloys which have been rolled with severe cold working frequently have initial permeabilities of less than 1000, a very fiat course of'the permeability curve measured in low-magnetic fields and increased coercive force. Such alloys having unsatisfactory properties may be greatly improved by slight cold working accord.- ing to this invention. For example a band which has been cold rolled without intermediate annealing, has,-after having been wound onto a core and after the core has been annealed, an initial permeability of only 1000. Even the very the band from-the core and rewinding it causes, after a repeated annealing, an increase in j the initial permeability to 6000, a very steeply ascendingpermeability curve and a coercive force down to 0.02 Oersted. More severe cold workin as for example slight stretching or reduction in cross-section, as for example by rolling down by less than about 20 per cent, also effects as improvement of the magnetic properties by a multiple (see the statements in Example 2 below). 7 According to this invention especially favourable magnetic qualities are obtained by selecting a comparatively high temperature, preferably from 1100 to 1200 C. for the final annealing. It is preferable to employ in the final annealing a temperature which is higher the lower the temperature employed in the previous annealing. For example if the previous annealing is carried out at 800-C., the initial permeability is 2000, the permeability for 0.02 Oersted is 10500 and the coercive force is 0.06 Oersted when the final annealing is carried out at 900 C. and the corresponding values are 6000,41000 and 0.031 when the final annealing is carried out at 1200C.

It has been found of special advantage to employ the process according to this invention for alloys which have been prepared by pressure and/or heat treatment without melting from metal powders obtained from the corresponding metal carbonyls by thermal decomposition.

The favourable magnetic properties obtained according to this invention render nickel-iron alloys containing from 40 to 50 per cent of nickel especially suitable for example for the construction of precision measuring transformers because these alloys combine in themselves a high permeability with weak fields, a very low coeroive power with high saturation and a high electrical resistance.

The following examples will further illustrate the nature of this invention but the inventio is not restricted to these examples.

Example 1 An alloy containing 50 per cent of nickel and 50 per cent of iron is prepared from the metals obtained from their carbonyl compounds, by sintering the powdery mixture. The sinter block is consolidated under a forging hammer and then worked up into a strip by hot and cold rolling;

the cold working after the last intermediate annealing in this treatment results in a reduction in cross section of 80 per cent. The strip is then subjected to a softening annealing for definite thicknessbysubjectingittoacoldworkfour hours at 1100 C. in an atmosphere of hydrogen (Sample I). A part of the annealed strip is further cold worked to the extent of 10 per cent (Sample 11), and another part of the strip is cold worked to the extent of 5 per cent (Sample III) reduction in cross section. All three strips are then wound in the same way onto cores while strewing with magnesia powder and. annealed for four hours in hydrogen at 1100 C.

The initial permeability is always extrapolated from measuring values down to below 0.001

Oersted. I

Example 2 An alloy containing 50 per cent of nickel and 50 per cent of iron is prepared by sintering the metal powders obtained from carbonyls, consolidated by forging andthen worked up into a strip by hot rolling and subsequent cold rolling with a 90 per cent reduction in cross section without intermediate annealing. The strip is wound into cores which are then treated in the following man-,

ner, the annealing always being carried out in an atmosphere of hydrogen:-

11M 15??? c i y or mum oerc ve Tmmt 0.02 Oerpermeaiorce ma bility Core of strip annealed at I 11W 0 1N0 18m 1163) 0. 081 Annealed at 1100 0., un-

wound, rewound, and I annealed at 1100 0-.-- 3000 8M0 134800 0. 024 Annealed at 1100 0..

slightly stretched and annealed at 1100 C.. 4000 36000 84100 0.03% Annealed at 1100 0., rolled 6 per cent and annealed at 1100 C- 4300 26000 95300 0. 033 Annealed at 1100 0.. rolled 17 per cent and annealed at 1100 0-.-- 5000 M500 107400 0. 040 Annealed at 1100 0.,

rolled 22 per cent and I annealed at 1100 0.-.. 3000 9000 61600 0. 056

What we claim is:

1. A process for the production of magnetizabie alloys substantially consisting of nickel and iron which comprises reducing the raw material to its definite thickness by subjecting it to a cold working of, more than per cent, then to a softening annealing, then to a slight cold working and then to a final annealing.

2. A process forthe production of magnetizable alloys substantially consisting of nickel and iron which comprises reducing the raw material to its ingoffrOmaboutto90percent,thentoa softening annealing,.then to a slight cold workwhich comprises reducing the raw material to its definite thickness by subjecting it to a cold working of from about 80 to per cent, then 7 to a softening annealing, then to a cold working alloys of nickel and iron ofless than 20 per cent, and then to a final annealing.

. 4-. A process for the production of magnetizable alloys substantially consisting ofnickel and iron which comprises reducing the raw material to its definite thickness by subjecting it to a cold working of from about'80 to 90 per cent, then to a softening annealing; then to a cold working not much stronger than that above which a recrystallization is caused by annealing and then to a final annealing. I a

5. A process for the production of magnetirable alloys substantially consisting of nickel and iron which comprises reducing the raw material to its definite thickness by subjecting it to a cold working of more than 60 per cent then to a softening annea n then to a slight cold working and then to a final annealing above the recrystallization 7 temperature. I I

6. A process for the production, of ma'gnetizable alloys substantially consisting of nickel and iron which comprises reducing the raw material to its definite thickness by subjecting it'to a cold working of more than 60 per cent, then to a softening annealing, then to a slight cold working and then to a final annealing at a temperature between about 1100 and about 1200 C. I

7. A process for the production oi. magnetizable alloys substantially consisting of nickel and iron which comprises reducing the raw material, prepared by heat treatment without melting from 8. A process for the production of magnetizable alloys-containing of from 40 to 50 per cent of nickel and of from 60 to 50 percent of iron which comprises reducing the raw material to its definite thickness by subjecting it to a cold working amna'r HEINZEL. manz num'scmam. 

